Keratometry is used in medical imaging to measure the contours of a surface. For example, keratometry may be used to measure the curvature of the outer surface of the cornea of an eye. A keratometry instrument exposes the eye to a light source and measures the reflections off of the outer surface of the cornea to determine the curvature. Typically, keratometry is used to determine the contour of the outer surface of the eye and is not used to determine the contour of surfaces deeper in the eye.